1. Field of the Invention
This invention relates to an on-line instrument that is able to sample the contents of a dense paste-like material, isolate the material, measure the material's rheological properties by extruding it under pressure and perform a self-cleaning operation. Such structures of this type, generally, provide precise measurements of the material's rheological properties (deformation and flow under pressure) such as yield stress, yield pressure, viscosity or Bingham number.
2. Description of the Related Art
It is known to employ devices for measuring properties of powdered or granular materials. Exemplary of such prior art is U.S. Pat. No. 4,607,532 ('532) to J. R. F. Arthur et al., entitled "Apparatus for Determining the Behavior of Powdered Material Under Stress". While the '532 device is capable of measuring the properties of powdered or granular materials, these materials are vastly different from dense paste-like materials, such as carbon.
It is also known to employ various rheological apparatus which are capable of measuring various materials. Exemplary of such prior art are U.S. Pat. No. 4,238,952 ('952) to R. Koopmann et al., entitled "Method of Determining Characteristic Rheological Quantities of Visco-Elastic Materials" and U.S. Pat. No. 5,269,190 ('190) to O. Kramer et al., entitled "Apparatus for the Performance of Rheological Measurements on Materials". While the '952 reference teaches a device that is capable of measuring certain rheological properties of visco-elastic materials, such as rubber compounds, this device is not capable of providing information regarding the onset of flow as a function of pressure, i.e., yield pressure. Also, while the '190 reference employs the use of rheological measurements, these are measurements of material creep and stress relaxation by the loading of a test specimen in an axial manner and not yield pressure.
Finally, it is known to employ capillary rheometers. Exemplary of such prior art are U.S. Pat. No. 5,172,585 ('585) to W. Gleissle, entitled "Continuously Operating Capillary Rheometer Apparatus with Minimized Response-Time Lag" and U.S. Pat. No. 5,417,106 ('106) to C. P. Grudzien, Jr., et al., entitled "Capillary Rheometer Plunger Pressure Transducer and Measurement Technique". While these references teach various capillary rheometer apparatus, they are concerned with measuring properties of polymer melts which are vastly different materials from a dense paste-like material, such as carbon.
It is apparent from the above that there exists a need in the art for an apparatus which can measure the rheological properties of dense paste-like materials and which is capable of providing information regarding onset of flow as a function of pressure.
It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.